I've recently realized that I don't have a lot of large vases in the house. Just a bunch of small ones that I like to buy in a set of three. Hmmm...
I really don't have a reasonable explanation for this behaviour. I only know I love to place my vases in a repetitive pattern: three vases in a straight or triangular line.
The other option is having just one small vase like this blue one from Ikea. But the only reason I bought it is because Ikea has two other vases and together they form a trio.
Next time I go to Ikea I will probably buy both.